linux-kernel - Re: [PATCH next 3/4] blk-mq: user (1 << order) to implement order_to

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Message-ID: <CACVXFVMFuiHpM-bVjyutP7fH621Gt0bo2+HLwRbk_aGsiZ+1Vw@mail.gmail.com>
Date:	Fri, 18 Apr 2014 23:47:51 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Jörg-Volker Peetz <jvpeetz@....de>
Cc:	Jens Axboe <axboe@...nel.dk>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH next 3/4] blk-mq: user (1 << order) to implement order_to_size()

On Fri, Apr 18, 2014 at 3:03 AM, Jörg-Volker Peetz <jvpeetz@....de> wrote:
> Ming Lei wrote, on 04/17/2014 17:49:
>> Signed-off-by: Ming Lei <tom.leiming@...il.com>
>> ---
>>  block/blk-mq.c |    7 +------
>>  1 file changed, 1 insertion(+), 6 deletions(-)
>>
>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index baff2d0..1eff3d9 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -1130,12 +1130,7 @@ static void blk_mq_free_rq_map(struct blk_mq_tag_set *set,
>>
>>  static size_t order_to_size(unsigned int order)
>>  {
>> -     size_t ret = PAGE_SIZE;
>> -
>> -     while (order--)
>> -             ret *= 2;
>> -
>> -     return ret;
>> +     return (1 << order) * PAGE_SIZE;
>
> Shouldn't this be
>
>         return ((size_t)1 << order) * PAGE_SIZE;
>
> ?

IMO, it isn't necessary since compiler will cast type
of 1 and the expression to size_t automatically.


Thanks,
-- 
Ming Lei
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